Monday, March 9, 2015

Armchair rockpooling

Felt a sudden urge to do a bit of rock-pooling at the weekend so called in at Marsden bay near South Shields, to see it there was anything interesting on the shore. This is an exposed coast and it's early in the season so were weren't expecting to find much.

There were plenty of common limpets on top of the rocks and ...

..... lots of chitons aka polyplacophorans aka coat-of-mail shells underneath rocks. But not a lot else. It was freezing cold and blowing a gale, which dimmed my enthusiasm when my hands began to turn blue. So I collected a small tuft of red seaweed that I found growing in a rock crevice and carried it home in a vial of seawater (about an egg cup-full) for a closer look under the microscope, in the comfort of an armchair.Spring comes to the coastal waters just like anywhere else, but it's not immediately obvious until you look really closely. As the spring plankton bloom progresses numerous small animals settle out of the plankton onto the shore, especially amongst the fronds of small red seaweeds that begin to grow now.

To go rockpooling in comfort, all you need is one of these - a binocular microscope with a zoom range between x7 and x45. It costs about as much as an entry level digital SLR camera and can provide hours of amusement.

Almost immediately I found these attached to the seaweed - tiny hydroids, waving their tentacles in the air, until the slightest tremor .....

... sent them into contractions

Then there were these minute mussels, translucent but beginning to acquire their darker pigment at their base, that were anchored to the seaweed after the mussel larvae had settled out of the plankton.

This little animal is an isopod crustacean, hard to spot amongst the seaweed fronds, but best of all there were ...

Their compound eyes are particularly striking, as are the highly reflected patches embedded in their exoskeleton

This tiny seaweed microcosm was home to about 20 of these gammarids, some of which had highly reflective, sparkly eyes.

The exoskeleton is this one contained small reflective patches that looked like interior lighting and it had eyes that glowed.

Aside from the mussels, gammarids, hydroids and isopods I also saw a minute sea slug and a flatworm, as well as copepods. The photos aren't very good (they were taken by holding a pocket compact camera up against the eyepiece of the microscope) but they do illustrate the wealth of microscopic marine life that's present even on exposed shores, down at the bottom of the inshore marine food chain. And at this time of year it's the most comfortable way to go rock-pooling.

Thanks Kate. The camera that I used is an old pocket camera called a Pentax W30 (there are more recent, better equivalents). It's actually waterproof (designed for used by surfers and other rugged outdoor types) so you can use it underwater in tide pools, but the benefit of this design is that it has internal focussing, which means that if you zoom it out and hold it up against the microscope eyepiece you can use it to take pictures down a microscope. Some smartphone cameras will probably work well like this too (I don't have a smartphone, but other people who do have tell me it works). Good hunting!

They are all wonderful, that's a lot of biodiversity in that small seaweed. When in NZ i was amazed that there are chitons also there, all along i thought they are only in tropical waters because we have them here. I read they are very old creatures maybe together with the dinosaurs? Lastly, i envy your binocular microscope. I wish i have someone nearby to borrow it from so i can hybridize my hoyas, haha! Pollinating it is so difficult that magnifying glass cannot help. ..Andrea

Hi Andrea, I think your chitons in tropical waters are much more colourful and much larger than ours! Sounds like you need something like this http://tinyurl.com/oxeooez for pollinating your Hoya flowers

The little Pentax camera that I used produces noisy images with the low light levels and they get worse if you sharpen them, but it's convenient and I can't afford a microscope with a proper camera attachment. I think some modern smartphone cameras would work better.

The photos are pretty good. I've not done much good with that approach. Good quality microscope cameras seem to be expensive, plenty of cheaper ones but they don't seem much better than these shots. Recently I've been playing with a video camera on my microscope to try to get some video.

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